Biochemically well-defined platelet plasma and granule membranes will be isolated by the refinement of currently used techniques and introduction of innovation for fractionating platelets. The study will continue to test external labeling techniques and other approaches in order to discover reliable plasma and granule membrane markers. Isolated platelet membranes will be used to obtain specific information about membrane structure and function. Plasma and granule membranes will be analyzed for differences in phospholipid and glycolipid composition and structure. The study will also continue to study the structure and function of platelet plasma membrane glycolipids and phospholipids by using intact platelets. The structural arrangement and function of plasma membrane phosphatidylethanolamine and phosphatidylserine will be probed by the selective modification of these lipids by enzymes, e.g., phosphatidylserine decarboxylase. The role of glycolipids in platelet function will be investigated by analyzing glycolipid membrane structure in platelets from normal individuals and from patients with hereditary and acquired platelet disorders.